1. Field of the Invention
The present invention relates to a method and apparatus for controlling directional sound sources based on a listening area, and more particularly, to a method and apparatus for allowing a user to listen to sound only in a listening area by maximizing a sound energy difference between a listening area and a non-listening area while maximizing sound radiation efficiency of each sound source.
2. Discussion of Related Art
Using typical speakers to output sound causes auditory disturbance to third parties due to a natural radiation characteristic of the sound. This has led to use of personal sound systems such as headphones and earphones, which do not cause substantial auditory disturbance to third parties and do protect personal privacy, but have an issue of sensory occlusivity. Accordingly, there is a need for a personal sound system capable of resolving the issue of sensory occlusivity without causing auditory disturbance to third parties.
A method for controlling a sound output direction by adjusting a delay time of a line speaker array has been disclosed. However, this method is limited in directional control because it does not consider a changing position of a listener.
To solve this problem, a sound control method capable of simultaneously forming quiet and loud areas by differentiating sound pressure levels for areas set by a listener in one sound area has been disclosed.
In the sound control method, sound energy is concentrated in an area where a user is located such that a bright sound area having a relatively higher energy density than other areas is formed, and a quiet area or a dark sound area having a relatively lower position energy is formed in the other areas.
However, strictly speaking, the sound control method is not intended to maximize the sound radiation efficiency of each sound source because sound energy of a predetermined area is formed as brightly as possible while the other area is formed as darkly as possible when each sound source has a limited size.
When a listening position of a listener is repetitively switched between two points (e.g., a sofa and a desk), sound energy must be repetitively calculated to maximize a brightness ratio between the bright area and the other area. This increases an amount of computation.